Field of the Invention
The inventive subject matter is directed towards the broad field of electrical water barriers to stun and repel fish in general and a unique matrix array electrode geometry.
Background
Electricity has been used to stun, capture, or modify the behavior of fish for more than one-hundred years. Various means of developing and controlling electric fields in water have been tried, with varying degrees of success.
The effect of electric currents on fish are well known in the prior art and as described in the prior art of electrofishing. Electrofishing involves the use of electric currents to attract and/or repel fish with the intent of creating aquatic barriers, sample fish populations, and/or to increase collection yields.
It has been established that relatively small potentials impressed across the body of a fish will result in a flight reaction in the fish (e.g. the fish will swim away from the electric field). An increase in the electric potential impressed across the fish results in a physiological response and alignment of the fish with the electric current, or electrotaxis. Still larger potentials may result in unconciousness or complete euthanasia of the fish.
Electrofishing barriers have traditionally been used in freshwater lakes and streams and are the subject of U.S. Pat. Nos. 5,445,111; 5,327,854; 4,750,451; 4,672,967; 4,713,315; 5,111,379; 5,233,782; 5,270,912; 5,305,711; 5,311,694; 5,327,668; 5,341,764; 5,551,377; and 6,978,734, which are incorporated herein by reference. Also, electrofishing has been used to stimulate yields of fishing in conjunction with the use of trawl nets as described in U.S. Pat. Nos. 3,110,978 and 4,417,301, which are also incorporated herein by reference.
Systems for controlling electricity in aquatic environments have been described in U.S. Pat. No. 5,460,123, which is incorporated herein by reference.
Furthermore, it has been shown that electrical gradient fields can be used to prevent mammalian predators from preying on salmonids. As was described in the paper, “Evaluation of an Electric Gradient to Deter Seal Predation on Salmon Caught in Gill-Net Test Fisheries” (North American Journal of Fisheries ManagementVolume 29, Issue 4, 2009), this paper describing an electric deterrent system was tested as an effective and safe method of deterring predation by Pacific harbor seals Phoca vitulina richardsi on sockeye salmon Oncorhynchus nerka and pink salmon Oncorhynchus gorbuscha caught in a Fraser River gill-net test fishery. These seals were deterred from foraging in a test fishing gill net in the Fraser River by using a pulsed, low-voltage DC electric gradient.
Also there has been further interest in using low voltage gradient fields to simultaneously guide salmonids, but also deter pinnipeds. (See the publication—Influence of a low intensity electric sea lion deterrence system on the migratory behavior of fishes in the upstream migrant tunnel at Bonneville Dam by Matthew G. Mesa, Ph.D. U.S. Geological Survey, submission date Oct. 1, 2009.)
Therefore in the prior art, a considerable body of work is associated with the electrification of large bodies of water to impress electric fields across larger fish, such as salmon or trout. Furthermore, the use of electricity to entrain and/or repel fish is not limited to salmon or trout, but may be used on almost all aquatic species.
Large arrays of vertically oriented electrodes have been used to provide a more or less uniform electric field in the upstream/downstream direction over the entire channel width. Some designs incorporate additional downstream electrodes to produce a weak graduated field for approaching fish. Three phase alternating current designs use the varying voltage and phase relationships between electrodes to provide a rotational vector field, and to help fill gaps in the field produced when the number of electrodes used is limited.
Surface, mid-water, and bottom mounted horizontal electrode arrays have been used to produce fields primarily oriented in the upstream/downstream direction, these fields can readily span the width of the stream. This type of array can provide minimal obstruction to avoid catching debris, and minimal interference with boat traffic (bottom mounted array). Horizontal arrays may be configured to produce a uniform field over a large area or produce a graduated field as required.
Small, movable arrays and electro-fishing boats have been developed to capture fish or move them to more desirable areas by herding.
Some of the common problems with existing electrode arrays (with the possible exception of moveable arrays) are the inability of the array to modify the electric field in order to optimize the field vectors for changing fish approach direction.
The present inventive subject matter proposes an array having a matrix of individually controlled electrodes which can be energized in combinations to produce a field oriented in any direction. The selected field direction would provide the required fish response utilizing the least power. The position of the field can be readily moved to herd fish from one area to the next and only the necessary sections need to be energized, reducing the power required to clear or maintain an area clear of fish.